Accumulators have been utilized between an upstream delivery station and a downstream receiving station to accumulate articles when the capacity of the downstream receiving station is either shut down or run at a speed wherein it cannot handle the number of articles being fed by the upstream delivery station. One particular accumulator is disclosed in U.S. Pat. No. 4,018,325. One problem with such accumulators is that the last article fed into the accumulator is the first article fed out of the accumulator and, as a result, it is difficult to keep track of the batch from which a particular article came from, and the sequence in which the articles are fed from the upstream delivery station.
Accumulators have been made wherein the first article in is the first article out. Such “first in, first out” accumulators are sometimes known as “FIFO” accumulators. For example, the owner of the present application is also owner of U.S. Pat. Nos. 6,152,291, 6,182,812, 6,230,874, 6,260,688, 6,382,398, 6,497,321, 6,523,669, 6,533,103, 6,550,602, 6,585,104, and 6,612,420, all disclosing various aspects of FIFO conveyors, and all incorporated by references herein for all purposes.
Various of the above patents disclose accumulators having conveyors extending along multi-level curved paths, with a transfer mechanism disposed between the conveyors for transferring the conveyed objects between the conveyors. Such accumulators are commonly called spiral accumulators. As disclosed, the transfer mechanisms of such spiral accumulators may be driven by rotatable members which contact the oppositely moving conveyors (or attachments thereto) at the point of transfer. The rotatable members travel with the transfer mechanism along the conveyors, at a position dictated by the relative speeds of the conveyors.